1. Field of the Invention
The invention generally relates to radio frequency receivers. In particular, the invention relates to techniques for mitigating the effects of interfering signals near in frequency to a desired signal.
2. Description of the Related Art
There are many types of data receivers in electronic equipment. Examples include wireless local area networks (WLAN), wireline networks, personal area networks, cell phone services, cable modems, DSL modems, satellite communications, and the like. Wireless systems, such as IEEE 802.11 for WLAN, IEEE 802.16 for broadband WirelessMAN, and Bluetooth for personal area networks, are particularly prone to interference from signals that are close in frequency to the signal that is actually intended to be received.
Two basic techniques are commonly used in the industry to handle interfering signals. In a first technique, the signal magnitude is compared before and after filtering to determine the presence of an out-of-channel interferer. In a second technique, the linearity of a radio frequency and/or baseband circuit is adjusted based on the signal level. Examples of these techniques are illustrated in, for example, U.S. Pat. No. 6,961,552 to Darabi, et al., U.S. Pat. No. 7,212,798 to Adams, et al., U.S. Pat. No. 6,498,926 to Ciccarelli, et al., and U.S. Pat. No. 7,079,825 to Wieck.